An Ultra-High Resolution Investigation of Environmental Signals at Colle Gnifetti, Swiss-Italian Alps

Abstract:

The Colle Gnifetti (CG) glacier saddle (4450m asl, Monte Rosa, Swiss-Italian Alps) is the only ice core drilling site within the European Alps suitable for archiving multi-millennial records in spite of its limited ice thickness (typically < 100 meters). Deciphering past climate signals in CG ice cores is particularly challenging due to rapid annual layer thinning and high glaciometeorological noise. As the latest addition to a unique multi-core array, our new ice core (drilled in 2013) is specifically designated for investigation using novel ultra-high resolution techniques in combination with traditional ice core analysis methods. Our novel technique - laser ablation (LA) inductively coupled plasma mass spectrometry (ICP-MS) produced > 8000 samples per meter for this project in comparison with the < 200 samples per meter achievable by the most state of the art continuous flow analysis (CFA) systems.

Here we present LA calcium (Ca) measurements from our new ice core in comparison with co-registered CFA Ca. This dual approach emphasizes the benefits of increased resolution in the deepest sections while simultaneously demonstrating that both systems capture similar trends in the more shallow sections, including annual layers of greater age than previously established at CG. Additionally, we further examine the composition of selected depth sections, initially found to contain anomalously high Ca, Na, or S, using LA, CFA, and liquid-ICP-MS measurement of discrete acidified meltwater samples. The comprehensive characterization afforded by the combination of all three techniques may enable us to classify the anomalies, quantify their frequency of occurrence and then speculate about the atmospheric conditions connected with such changes.